Process and apparatus for continuous three-dimensional forming of heated thermoplastic materials

ABSTRACT

Continuous process and apparatus form products from thermoplastic materials between top and bottom mold carriages. A flexible silicone rubber mold on a fiber belt continuously moves around each carriage frame. A surface of desired shape on one rubber mold mates with the desired shape of an opposed rubber mold forming a continuously moving mold channel into which is fed hot thermoplastic material at moldable temperature. After discharging the molded plastic product from the moving mold channel, localized surface heat in the molds resulting from contact with hot plastic is removed from the belt molds by air blown onto mold surfaces. Each carriage frame includes a back-up plate coated with low friction coefficient material over which slides a continuously moving belt mold. These slippery plates have numerous air-bearing holes feeding high pressure air between them and the respective moving fiber belt for reducing friction and wear. The fiber belts are guided and driven by a wide, central V-shaped toothed ridge or by twin, wide V-shaped toothed ridges along belt margins. These ridges fit into and mesh with corresponding toothed grooves of sprocket drive rolls, serving to maintain alignment of revolving mold belts. An electric drive motor, with or without torque-motor assistance, revolves both belt molds in unison maintaining their mating alignment. Electric screw jacks raise the top carriage, extend/retract grooved exit rolls, fine-tune alignment of revolving belt molds by adjusting grooved exit rolls and adjust the machine relative to the extruder.

This application is a division of application Ser. No. 07/506,072, filedApr. 6, 1990, now U.S. Pat. No. 5,167,781.

FIELD OF THE INVENTION

The present invention relates generally to plastics molding and moreparticularly to a continuous process and apparatus for forming productsfrom thermoplastic materials between top and bottom mold carriages. Eachcarriage has a frame including a backup plate coated with a lowcoefficient of friction material over which slides a continuously movingbelt mold. The belt mold is comprised of a silicone rubber mold adheredto a fiber belt. The silicone rubber mold has a surface of desired shapefor with an opposed mold surface to form a continuously moving moldchannel into which is fed moldable thermoplastic material. After moldingand cooling the hot plastic material, localized surface heat of the beltmolds is removed as the belts return to the entry end of the machinethrough ducts of cold air moving in the opposite direction.

BACKGROUND OF THE INVENTION

An apparatus and process for forming products from thermoplasticpolymeric material having three-dimensional patterns and surfacetextures is disclosed in U.S. Pat. Nos. 4,128,369 and 4,290,248, both ofwhich are hereby incorporated by reference.

In the apparatus and process disclosed in said patents a thermoplasticmaterial to be formed is heated above its glass transition temperaturebefore introduction between travelling flexible belt molds, whichrevolve in opposed relationship. The flexible belt molds each include athin, flexible sheet-metal belt of relative high thermal conductivityand form a traveling mold channel, at least one having a flexiblethree-dimensional pattern formed on its front face. Opposed nip rollspress the revolving belt molds against the entering thermoplasticmaterial. At least one belt mold travels partially around the nip rolland impresses its three-dimensional pattern into the heated plasticmaterial in a progressive localized rolling, squeezing action in the nipregion. Thereafter, a series of backup rolls along the mold channel holdthe traveling belt molds against the impressed material for maintainingthe impression while being cooled by liquid coolant into thememory-retention state. A cooling liquid, mainly water at roomtemperature, is moved along the backup rolls and applied to the backsurface (inside surface) of each thermal conductive steel belt forcooling each belt mold. After the plastic material has been sufficientlycooled to retain three-dimensional patterns, the flexible belt molds areseparated from it. Large area architectural panels can be produced. Beltmolds are shown as including wide, thin, endless, flexible metal belts,at least two-feet wide, having a wide flexible mold formed of aheat-resistant material, such as rubber, bonded to the metal belt.

The prior disclosed apparatus utilizes thin steel belts which revolveupon large flat surface drive pulleys. Steel belts suffer from theinherent problems of being susceptible to dents, crimped edges, andrust. They also require a weld seam. Steel belts present difficulties inthe maintenance of alignment as they travel over flat surfaced metalpulleys.

Steel belts are susceptible to denting, crimping, rusting, and camberbecause they are extremely thin, being typically 0.025 to 0.075 of aninch thick. The use of such extremely thin steel belts in an industrialenvironment increases the probability of incurring damage thereto.

The use of a metal belt requires that the drive pulleys be comparativelylarge because the metal belt cannot be made to continuously travel oversmall-diameter pulleys. Small pulleys cause bend-yield-stress elongationof thin metal belts. Thus, the drive pulleys in the prior disclosedapparatus must be fabricated of a sufficient diameter to accommodate themetal belt and consequently the drive pulleys occupy a substantialamount of space within the disclosed machine. Thus, the space availablefor cooling and other apparatus is strictly limited.

A weld seam is required in the formation of an endless-loop metal belt.An elongate planar sheet of metal is looped about itself and weldedtogether to form the belt, thus forming a weld seam. The formation ofsuch an endless-loop metal belt, without damaging it, is necessarily atime-consuming and somewhat difficult task. The weld seam should be madeto keep the belt edges parallel to each other and be ground flush toprevent distortion of the flexible rubber mold which is to besubsequently formed on the outer surface of the welded planar metalbelt.

Further difficulties in the maintenance and alignment of the metal beltof the apparatus disclosed in said patents occur because the metal beltis installed upon flat pulleys which lack any self-aligningcharacteristics.

Sixty or more small-diameter rollers function to maintain the twotravelling mold surfaces of the prior art apparatus in close contact.The small-diameter steel rollers rotate continuously and arecontinuously exposed to the liquid coolant, which is comprised mainly ofwater. They ar subject to frequent malfunction and require periodicmaintenance. Also, the use of such numerous small-diameter rollers doesnot facilitate maximum intimate contact of the opposing travelling moldsurfaces because of the many gaps inherently formed between suchrollers. The multiplicity of these steel rolls causes the travellingflexible molds to experience considerable fluctuations in contactpressures as they successively travel over roller-gap-roller-gap-roller,etc.

In the prior disclosed apparatus, an offset is formed between the insideedge of the exit rollers and the path of the molded product to helpstrip the belt molds from the molded product. That is, the circumferenceof each exit roller is not tangential to the plane of one surface of themolded product path, but rather the bottom roll is downward and theupper roll is upward away from the molded product path, in order to helpseparate the belt molds from the molded product. This offset reduces thesupport provided to the molded product, thereby requiring that themolded product be sufficiently cooled and rigid to resist deformationprior to passing between the exit rollers.

The prior disclosed apparatus utilizes hydraulic actuators to tensionthe mold belts, provide a compressive force to maintain contact of thetwo opposing mold belts, and to lift the upper mold assembly off of thelower mold assembly to facilitate maintenance and the changing of moldbelts.

As is well known in the art, hydraulic actuators require the use of amotor, pump, various hoses and valves, and actuator cylinders. Thehydraulic system must be maintained in a leak-free condition in order tofunction properly and prevent contamination of the molded product.Hydraulic systems constantly consume electrical energy when theapparatus is operative. That is, the hydraulic motor and pump mustconstantly be running in order to provide pressure to maintain andchange position of the hydraulic actuators. The motor and hydraulic pumpare inherently noisy and commonly located in close proximity to theapparatus. This makes the working environment of the apparatus extremelyuncomfortable and contributes to an unsafe and unhealthy workingenvironment.

The prior art discloses an apparatus and process that primarily removesthe heat of the hot plastic by moving cold water along the smalldiameter backup rolls against the backside of the thin steel belts. Thisback-surface water cooling method proves inefficient because the heat ofthe plastic must first pass through the thick low thermal conductivesilicone mold on at least one belt mold. The silicone mold material hasa low thermal conductivity with a K factor of about 0.10 compared withthe mild carbon steel which has a K factor of about 26.0. The K factorvalues for the materials are expressed in units of BTU per hour througha square foot per degree Fahrenheit of temperature difference per foot.

In addition to the difficulty of removing the heat of the plasticthrough the low thermal conductive silicone, this prior art back-surfacemethod of cooling did not provide the means to control the temperatureof the belt molds. It is desirable for good molding conditions to havethe belt molds consistently at about the same temperature as the moldsfirst contact the hot plastic each time they return to the entry end.

The back-side fluid cooling method also involves a water sump under themachine; a water cleaning system; water chillers or water cooling tower;and a water recirculating system. This equipment needs constantmaintenance, causes high humidity in the work place, and increases thecost of operating the machine.

Therefore, the prior disclosed apparatus and process has a variety ofdeficiencies which detract from its effectiveness, efficiency, andmarketability. In view of the shortcomings of the prior disclosedapparatus, it is desirable to provide an apparatus and process whichdoes not utilize thin steel belts and consequently is not susceptible tocrimps and dents; does not have weld seams; is not susceptible to rustand camber; and does not have difficulties in the maintenance ofalignment as it travels over flat surfaced pulleys. It would bedesirable to provide an apparatus with belt molds that can include aridge and a gear or cog arrangement that will fit and mesh with amatching grooved drive roll sprocket as a means of maintainingmechanical alignment, both laterally and in the forward motion feedingdirection. It would also be desirable to provide an apparatus which doesnot use a plurality of small-diameter rollers to maintain intimatecontact of the upper and lower belt molds. These rolls require periodicmaintenance as they are subject to the effects of wear due to frictionand to exposure to the coolant water being applied to the steel belts.

Further, it would be desirable to provide an apparatus which usessmall-diameter entrance and exit rollers to reduce the length of themold belts required, increase the space available for cooling and otherequipment, and reduce the size and cost of the machine as a whole.

Further, it would be desirable to provide an apparatus which does notrequire the use of hydraulic actuators and consequently would eliminatethe need for a motor, pump, various hoses and valves, and actuatorcylinders, as well as the requirements for maintaining these items in aleak-free state. It would also be desirable to provide an apparatuswhich operates quietly and does not constantly consume electricalenergy.

Further, it would be desirable to provide an apparatus which does notutilize an offset between the exit rollers and the plane of the productpath so that support is continuously provided to the molded product asit travels the length of the machine onto the product conveyors.

Further, it would be desirable to provide an improved means andapparatus to remove the heat from the surface of the silicone molds.Extracting the heat through the silicone and the steel belt backing withcold water moving against the thin steel backing is an inefficientexchange of heat and limits production rates. Further, it improves themolding operation if the heat of the belt as it first contacts the hotplastic is controlled. This can be accomplished by controlling thecooling of the belt molds through a series of dampers in the cold airducts that provide the means to vary the temperature of the molds byvarying the amount of chilled air blowing on the belt molds as well asthe ability to control when the belt molds will be cooled on theirreturn to the entry end of the machine.

SUMMARY OF THE DISCLOSURE

The following description and drawings disclose a new, improved processand apparatus for the continuous forming of products from thermoplasticpolymeric material having three-dimensional patterns and surfacetextures.

The process and apparatus described in U.S. Pat. Nos. 4,290,248 and4,128,369 was disclosed eleven and thirteen years, respectively, priorto this application. Since then much has been learned, product designspecifications have become more demanding, and new technology has becomeavailable. The apparatus and process embodying the present inventionproduce a molded plastic product having closer tolerances on aless-costly machine. The machine is easier to maintain, uses lessenergy, is less expensive to operate, and is quieter in operation.

The present invention specifically addresses and alleviates theabove-mentioned deficiencies associated in the prior art. Moreparticularly, the present invention provides a continuous process andapparatus for forming products from thermoplastic materials between topand bottom mold carriages.

Each carriage has a frame including a backup plate coated with a lowcoefficient of friction material over which slides a continuously movingbelt mold. The belt mold is comprised of a silicone rubber mold adheredto a multi-ply woven fabric belt made of non-metallic fibers. Thesilicone rubber mold has a surface of desired shape for mating with anopposed mold surface to form a continuously moving mold channel intowhich is fed moldable thermoplastic material.

After molding the hot plastic material, surface heat localized in thesurfaces of the belt molds is removed by cold air blowing from one ormore air conditioning units directly onto the mold surfaces, preferablyat temperatures about 35° F. to about 50° F. The cold air is directed bya series of dampers in the air ducts to blow counter to the directionthe belt molds are travelling and to cool the belt molds as desired incertain zones cf their return to the entry end.

The low coefficient of friction backup plates have numerous air-bearingholes for feeding high-pressure air between the low coefficient offriction plates and the moving fiber belt to provide an air-bearingeffect to reduce contact pressure and friction.

The fiber belts are guided and driven by a wide V-shaped central ridgeor by twin V-shaped wide ridges near their edges. The V-shaped ridgesfit into and mesh with corresponding grooves of the sprocket drive rollsand operate to drive the belts and to maintain alignment of the beltmolds. An electric drive motor, with or without the assistance of atorque motor, drives both belt molds in unison to maintain theirrelative alignment. Electric screw jacks raise the top carriage, extendor retract the grooved exit rolls, and fine-tune the alignment of themoving belt molds by adjusting the grooved exit rolls.

The use of fabric belts eliminates weld seams, crimps, dents, and rust.The use of fabric belts also eliminates many of the alignment problemsassociated with the prior art steel belts. Additionally, the use offabric belts permits the use of smaller diameter pulleys, thus providingmore room for cooling and other equipment. The use of smaller diameterpulleys also reduces th required length of the mold belts.

The use of a low coefficient of friction backup plate with air bearingseliminates the requirement for a plurality of small-diameter rollers.The backup plates stabilize the flexible travelling mold channel inheight, configuration, and orientation, and provide belt contactpressure consistently as the flexible belt molds travel from the entryto the exit end of the machine. In addition, the associated problems ofwear due to friction, the significant manufacturing costs, and theassociated maintenance requirements are likewise eliminated.

The screw jacks used in the machine embodying the present inventionoperate quietly, consume power only when being used, and provideprecision positioning of the moved parts. The screw jacks thus eliminatethe problems associated with the prior art use of hydraulic actuatorswhich require a motor, pump, various hoses and valves, and actuatorcylinders; must be maintained in a leak-free state; operate loudly; andconstantly use energy when running.

The use of small drive rolls, instead of the larger pulleys required bythe use of steel belts in the prior art, makes it possible to constructa machine incorporating the present invention in a simpler and lessexpensive manner. The use of smaller diameter rolls makes maintenanceand handling of the upper carriage substantially easier; provides roomfor cooling apparatus; and reduces the required length of the mold belt.

In a machine embodying the present invention, the exit rolls are mountedin the same plane as the plane of the molded product and thus providesupport to the molded product as it passes between the exit rolls to theproduct conveyor.

The exit rolls in a machine that embodies the present invention may alsobe crowned to aid in alignment of the fabric belt, thus simplifyingmaintenance and operation.

Air cooling is effective due to the use of counter-current-flow and afabric belt. The use of counter-current-flow provides maximum heatexchange between the heated mold surface and the cooling air. The fabricbase, has a low heat capacity and low thermal conductivity similar tothe silicone molds. It therefore operates to keep the heat absorbed fromthe hot plastic near the surface of the belt mold where it may bereadily extracted by cold air directly impinging against the moldsurfaces.

The process steps and apparatus components that are improved, and themeans of achieving the desired improvements, are shown and described asfollows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of the new, improved apparatus for thecontinuous forming of products from thermoplastic polymeric material,with certain parts being shown in section;

FIG. 2 is an enlarged partial elevational sectional view of the input orfront end of the apparatus shown in FIG. 1;

FIG. 3 is a cross-sectional view taken along the line 3--3 in FIG. 2;

FIG. 4 is a partial cross-sectional view taken along the line 4--4 onFIG. 1 showing one of the wide drive roll sprockets

FIG. 5 is a partial cross-sectional view taken along the line 5--5 onFIG. 1 showing a crowned and grooved exit idler roll;

FIG. 6 is a partial cross-sectional view similar to FIG. 4 for showing awide drive roll twin sprocket, which is an alternative to the drive rollsprocket shown in FIG. 4;

FIG. 7 is a cross-sectional view generally similar to FIG. 3 for showingan alternative twin-ridged fiber belt supported on a twin-channeledguide plate. This twin-ridged fiber belt is also seen in FIG. 6 beingdriven by the twin-drive sprocket shown in FIG. 6;

FIGS. 8A and 8B are cross-sectional views taken generally along theplane 8A--8A and 8B--8B through the apparatus of FIG. 1. (For clarity ofillustration, the mold belts have been removed in FIG. 8A The belt moldsare shown in section in FIG. 8B while components of the frame and drivetrain are omitted from FIG. 8B for clarity of illustration.);

FIG. 9 is a partial cross-sectional view through a pair of opposed fiberbelt molds which are properly aligned; and

FIG. 10 is a view similar to FIG. 9 for showing how the product isdeformed, when the fiber belt molds are not properly aligned.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The new, improved process and apparatus for the continuous forming ofproducts from thermoplastic polymeric material will now be described indetail with reference to the drawings. The same reference numbers areused in the various views to indicate the same components of theapparatus. Alternative embodiments of components of this apparatus aredescribed and shown.

FRAME

Referring now to FIGS. 1-3, 7, 8A, and 8B, a metal frame 20 (FIGS. 1 and8A) is comprised of steel side plates 21 (shown in FIG. 8A), backupplates 22 (FIGS. 1, 2, 3, and 7), and cross-bracing members 23 (FIG. 1).The motors 48 and 48A, wide sprocket drive rolls 43, backup plates 22,grooved exit rolls 51, air conditioners 76, and other auxiliaryequipment are mounted to this frame. The sides of the frame 20 may havelightening holes (not shown) to reduce their weight and provide easyaccess to wiring and miscellaneous mechanical and electrical equipmentmounted inside the frame 20.

The frame 20 that forms the sides 21 of the bottom carriage 25 (FIGS. 1,8A, and 8B) is joined at the top by the bottom backup plate 22B (FIGS.2, 3, and 7) and cross-bracing members 23 (FIG. 1). The bottom backupplate 22B and cross-bracing members 23 act as transverse stiffening webswhich greatly stiffen the frame 20 of the bottom carriage 25. Similarlythere is stiffening of the frame 20 of the top carriage 35, to bedescribed later, so that their side plates 21 (FIG. 8A) can be thinnerthan otherwise. One side of the bottom carriage 25 is joined to two(only one is seen in FIG. 8A) vertical rectangular tubings 24 (FIGS. 8Aand 8B) which are anchored onto a heavy metal floor base 26 (FIGS. 8Aand 8B). The floor base 26 may be fitted longitudinally with invertedangle irons 27 (FIGS. 8A and 8B), V wheels, or similar means of slidingor rolling the machine 30 (FIG. 1) away from the extruder 28 (FIG. 1) toallow space to provide extruder or mixer maintenance and to changeextruder dies 29 (FIGS. 1 and 2).

In operation, the machine position is adjusted as close as necessary tothe extruder feeding die 29 (FIGS. 1 and 2) to provide the belt molds 34and 36 with the melted plastic feed stock 77 (FIGS. 2 and 8B). Theheated melted thermoplastic material is moldable. If the product is tocontain foamed plastic, the foamed plastic being fed from the extruderfeeding die 29 (FIGS. 1 and is at an early stage of its foaming actionto control finished product density and to produce a quality product.

The frame 20 (FIGS. 1 and 8A) that forms the sides of the top carriage35 (FIGS. 1, 8A, and 8B) is stiffened by joining its sides 21 at thebottom by the top backup plate 22A (FIGS. 1 and 2) and cross-bracingmembers 23 (FIG. 1). One side of the top carriage 35 has two (only oneis seen) vertical slides 31 (FIG. 8A) that are housed inside the twovertical rectangular tubings 24 (FIGS. 8A and 8B). The top carriage canbe raised by electrical screw jacks 32 (FIG. 8A) up about eight inchesfrom its lowest position in which the top carriage 35 (FIG. 1) isresting against the bottom carriage 25 (FIG. 1) or against set pins onthe sides 21 of the bottom carriage 25.

It is necessary to raise the top carriage 35 to change the belt molds 34and 36 as required to produce a product of a different design orpattern. The top carriage 35 is held in a raised, cantilevered positionby the slides 3 (FIG. 8A) held inside the two vertical tubings 24anchored to the floor base 26. The top carriage 35 is lowered to bringthe top and bottom belt molds 34 and 36 (FIGS. 1 and 8B) together toform the mold channel 33 FIG. 8B) in which the melted plastic is formed,cooled, and set.

The wide rectangular air-bearing chambers 63 (FIGS. 1, 2, 3, and 7),described later, which extend the length of the top and bottom carriages35 and 25, respectively, as shown in FIG. 1 act as strong, widerectangular box beams which resist deflection and distortion of the moldcarriages 35 and 25. The side plates 21 can be less massive thanotherwise, because of the stiffening action of these air-bearingchambers 63.

On a machine embodying the present invention, as depicted in FIG. 1,fiber belts 37 and 38 are cooled by removing surface heat from the moldsurfaces 78 (FIG. 8B) of the top 39 and bottom 40 molds with cold airwhile the surfaces of molds 39 and 40 are moving adjacent to chilled airin ducts 74. Such cold air 79 is being blown in a direction counter tothe moving belt molds as the belt molds are returning from the exit endof the machine to the entry end, as will be explained in detail later.

Electrical screw jacks 56 provide positive and precise movement of thetop carriage 35 and of the grooved exit rolls 51. Screw jacks arepreferred to the prior art use of hydraulic jacks, since screw jacksonly consume electrical power when they are being used to effect achange in position. Hydraulic jacks, on the other hand, constantlyconsume power merely to maintain position since a hydraulic pump mustconstantly be driven by a constantly running electric motor.

The top carriage slide 31 provides a simple, perpendicular mating fit ofthe upper 34 and lower 36 belt molds and operates to open with astraight, vertical lift rather than in a clam shell fashion as occurs inthe prior disclosed apparatus.

The molded product 52 is further cooled as necessary by passing througha water bath or spray, or by passing through downstream air-coolingducts 84 (FIG. 1). The cooled finished product "P" is cut to length asit continues to travel by a cutting means 85 (FIG. 1), for example, ashearing, sawing, or similar device moving at the same speed as theproduct.

FIBER-BACKED BELT MOLDS

Fiber belts 37 and 38 (FIGS. 3, 4, 6, 7, and 8B) for the belt molds 34and 36 are each made of plies of woven fibers, such as nylon, polyester,or cotton, that are commercially bonded together. Both a four-ply wovencotton hot stock and water belt, Model 47, available from BeltserviceCorporation of Sacramento, Calif., and a four-ply woven polyester beltavailable from Sparks Belting Company of Pomona, Calif., have proven tobe satisfactory fiber backing for the endless belt molds 34 and 36.Fiber belts are preferred to prior art thin metal belts because fiberbelts provide a belt mold backing with true parallel edges and have noweld or camber, and they have only about one-hundredth of the thermalconductivity (K factor) as steel. Additionally, fiber belts will notdent, crimp, or rust, and are easier to store and handle.

The outer side of each of the top 37 and bottom 38 fiber belts (FIGS. 3,4, 6, 7, and 8B) has a rough stipple or cloth surface to optimize theadherence of the respective top 39 and bottom 40 silicone rubber molds(FIGS. 3, 4, 6, 7, and 8B). The rubber silicone molds 39 and 40 may becomprised of General Electric RTV664 silicone rubber, manufactured byGeneral Electric Company.

Another advantage of using a fiber belt instead of a thin steel belt isthat the inner side of the fiber belt 37 and 38 can have a wide,flattened V-shaped ridge 41 (FIGS. 4 and 5) or other shaped ridge, orhave a pair of spaced twin ridges 41 (FIGS. 6, 7, and 8B) that will fita matching groove 42 (FIGS. 4 and 5) or grooves 42 (FIGS. 6, 7, and 8B)in the sprocket drive roll 43 (FIGS. 1, 2, 3, 4, 6, 8A, and 8B). The useof at least one flattened V-shaped ridge 41 being received by matchinggroove 42 in the sprocket drive roll 43 provides mechanically positivetransverse (tracking or side-to-side) alignment of the belt molds 34 and36. Thus, the fiber belts 37 and 38 are mechanically held from driftinglaterally. This positive mechanical transverse alignment is notaccomplished with thin metal belts as shown traveling on flat-surfacedpulleys in U.S. Pat. Nos. 4,128,369 and 4,290,248.

The V-shaped ridge 41 also has a gear or cog configuration 47A (FIGS. 4,6, and 8B) that will fit a matching gear or cog configuration 47 in thegroove 42 of a positive drive roll sprocket 43 (FIGS. 4, 6, and 8B).Such a groove and gear or cog arrangement eliminates belt slippage andprovides forward-motion, feeding-direction alignment of the patterns onthe belt molds 34 and 36. A timing chain or timing belt 44 (FIG. 8A)connecting timing gears or timing pulleys 45 (FIG. 8A) on the shafts 46(FIGS. 8A and 8B) of the top and bottom drive roll sprockets 43 are usedto maintain this forward motion alignment of the pattern 78 (FIG. 9) ofthe top and bottom belt molds 34 and 36 such that the patterns 78 of thetop and bottom belt molds 34 and 36 move in unison from the entrance 89(FIG. 1) to the exit 90 of the machine 30. In other words, the patternson the two belt molds are caused to be moving forward at the same rateof travel with simultaneous, equal, synchronous forward motion.

Another advantage of using fiber belts is their ability to travel arounda sprocket roll of small diameter compared to the larger diameter flatsurfaced pulleys required to prevent bending-yield-stress elongation ofthin metal belts. Because fiber belts may travel around a diameter assmall as 6 inches, small drive roll sprockets and grooved exit rolls of6 inches to 16 inches in diameter are used to gain space for acompact-designed and efficient air-conditioning cooling system,especially in the limited space available for cooling equipment to coolthe bottom belt mold 40. The facility and convenience for changing thebelt molds 39 and 40 are also improved by utilizing the added availablespace obtained by using fiber belts 37 and 38 and small sprocket driverolls 43.

A further advantage of using fiber belts 37 and 38 is their low thermalconductivity that approximately matches the low thermal conductivity ofthe silicone rubber molds 39 and 40. For example, bonded fibers have a Kfactor of about 0.27 and the K factor of silicone rubber is about 0.10.By comparison, 1 percent carbon steel has a K factor of about 26, orabout one hundred times more than the fiber belts. The low thermalconductivity of the fiber belt and silicone rubber mold causes the heatof the hot plastics 77 (FIGS. 2 and 8B) to be retained on and near themold surfaces 78 for faster removal by the more efficient method ofusing cold, dry, moving air to directly cool these molding surfaces 78of the belt molds. The above K factor values for the materials involvedare expressed in units of Btu per hour through a square foot per degreeFahrenheit of temperature difference per foot for steel and for rubberand per inch for bonded fibers.

SPROCKET DRIVE ROLLS

The small diameter sprocket drive rolls 43 (FIGS. 1, 2, 3, 4, 5, 8A, and8B) are between 6 inches and 16 inches in diameter. The sprocket driveroll 43 has a single, central wide recess or groove 42 (FIG. 4) or apair of axially-spaced recesses or grooves 42 (FIGS. 6, 8A, and B), eachsuch groove having gear or cog teeth 47 which engage with matching gearor cog teeth 47A on the ridge 41 of the fiber belt 37 or 38 resulting ina positive mechanical transverse and longitudinal alignment of the beltmolds 34 and 36. The unison-forward-motion alignment, also calledlongitudinal alignment, is assured by connecting the shafts 46 (FIGS. 1,2, 3, 4, 6, 8A, and 8B) of the top and bottom drive sprockets 43 with atiming chain or belt 44 (FIG. 8A).

The small diameter sprocket drive roll 43 also allows more space formold changing and for air-conditioning equipment positioned between thefloor and the pass line of the extruded material, which is normally 39to 44 inches from the floor.

The sprocket drive rolls 43, shown in FIGS. 8A and 8B and that shown inFIG. 6, have twin-wide grooves 42 located near their opposite ends. Eachof these wide grooves 42 have gear or cog teeth 47 which engage withmatching gear or cog teeth 47A (FIG. 6) on the twin-wide V-shaped ridges41 located near opposite edges of the fiber belts 37 or 38. As shown inFIGS. 6 and 8B, the twin ridges 41 are disposed near the edges of thefiber belts 37 and 38 beyond the edges of the silicone rubber molds 39and 40. Those skilled in the art will recognize that other arrangementsof the V-shaped ridges 41 are suitable. In FIG. 6 the edge of the rubbermolds 39 or 40 is shown spaced inward a distance of "Z" from the edge ofthe fiber belt 37 or 38, and this inward spacing "Z" is greater than theoverall width of each V-shaped wide ridge 41.

SPROCKET DRIVE ROLL MOTORS

The top and bottom sprocket rolls 43 are driven by a D.C. motor 48 (FIG.8A). Sometimes a torque motor 48A and gear reducer 50A (FIG. 8A) areused to assist the drive motor. The torque motor helps to drive the loadbut does not override or fall behind the drive motor. This drive andtorque motor arrangement 48 and 48A prevents the motors from forcing thebelt molds 34 and 36 out of longitudinal alignment when two motors areused and maintains the integrity of the positive mechanical alignmentbetween the sprocket drive rolls 43 and the geared belt molds 34 and 36.A sprocket gear 91 on the shaft of the motor 48 drives a chain 49 (FIG.8A) for driving the sprocket gear 92 of a gear reducer 50 (FIG. 8A)connected to the shaft 46 of the bottom sprocket drive roll 43. If atorque motor 48A is used to assist the drive motor, a gearbox 50Aconnected to the shaft 46 of the top drive roll sprocket 43 is connectedto the torque motor 48A by means of chain 49A.

This arrangement of drive 48 and torque 48A motors provides for usage ofmotors of less horsepower that are less expensive to purchase andoperate when used with gear ratios, like 150:1, in the gear reducer 50and 50A to achieve the necessary belt operating speeds using lessenergy.

GROOVED EXIT ROLLS

The grooved exit rolls 51 (FIGS. 1 and 5) disposed at the output end ofmachine 30 are the same diameter and length as the drive rolls 43disposed at the input end of the apparatus, but are not motor-driven norgeared to each other. The grooved exit rolls 51 on shafts 54 (FIG. 5)are mounted to be aligned tangential to the slippery low coefficient offriction surface 59 (FIGS. 1, 2, 3, and 7) covering the backup plates22. By mounting each grooved exit roll 51 tangential to the slipperysurface 59 of the backup plate 22, open space without support is reducedbetween the backup plates and a product conveyor 53 (FIG. 1). The singleor twin grooves 42 in the grooved exit roll 51 are smooth, without gearor cog teeth.

The grooved exit rolls 51 may or may not be crowned (dimension "Y" inFIG. 5) and provide the means to fine tune the transverse (lateral)tracking alignment of the belt molds 34 and 36. For example, in thepreferred embodiment such crowning "Y" is in the range from about 1/64inch to about 3/16 inch per foot of axial length of the exit roll 51.One end of a shaft 54 of each of the top and bottom grooved exit rolls51 is held stationary during operation at a desired position with aself-aligning bearing 55 (FIG. 1). The desired position of this bearing55 can be adjusted backwards and forwards, arrow 86 (FIG. 1), by a firstelectric jack screw (not shown), but this bearing 55 is held stationaryduring running of the machine 30. The other end of the shaft 54 of eachgrooved exit roll 51 is in a self-aligning bearing 57 (FIG. 1) that canbe moved backwards and forwards by a second electric screw jack 56(FIG. 1) along slideways 58 (FIG. 1) to increase or decrease the belttension along one edge region, relative to the other edge region,thereby fine tuning the tracking of the belt molds as may be desired tokeep the belt molds 34 and 36 aligned with each other within thetolerances required by the mold pattern. Thus, the first electric screwjack (not shown) operates to set the overall tension on each exit roll51 and the second jack screw operates to align the longitudinal axis ofeach specific exit roll 51 perpendicular to the direction of travel ofthe molded product 52.

The product pattern is distorted (as seen by comparing FIGS. 9 and 10)if either the longitudinal alignment or transverse (lateral) alignmentis not maintained.

BACKUP PLATES

Backup plates 22 (FIGS. 1, 2, 3, and 7) are comprised of steel up to1-inch thick and are coated with a layer 59 (FIGS. 1, 2, 3, and 7) ofhigh or ultra-high molecular weight high-density polyethylene, Teflon,or other low coefficient of friction material having good lubricity andabrasion resistance.

The metal backup plate 22 coated with a material with excellentlubricity 59 provides an even, continuous level platen for supportingand guiding the belt molds 34 and 36 (FIGS. 1, 2, 3, 4, 6, 7, 8, 9, and10) to slide forward under a constant pressure thereby stabilizing theheight, configuration, orientation, posture, and belt pressure beingprovided consistently along the travelling, flexible, mold channel 33.

The backup plates 22 are shown drilled with a multitude of air-bearingholes 60 (FIGS. 2, 3, and 7), drilled at a 45-degree angle, aimed towardthe advancing belt mold, as shown in FIG. 2, and extending through thehigh-density slippery backup plate coating 59 (FIGS. 2, 3, and 7).

The air-bearing holes 60 (FIGS. 2, 3, and 7) are drilled to face forwardto meet the underside of the advancing fiber belts at 45 degrees,creating a friction-reducing lifting action when preferably ambienttemperature high pressure air 61 (FIGS. 1, 2, 3, and 7) is forcedthrough the holes by a blower 62 (FIGS. 1 and 7). It is believed thatforming the air-bearing holes 60 at an angle of 45 degrees to thesurface of the backup plate and orienting the air-bearing holes 60 suchthat air blows in a direction opposite the direction of the belt'stravel, maximizes the friction-reducing action of the air. There is alsoan analogous blower (not shown) for feeding an air chamber 63 (FIG. 1)in the top carriage 35. Each blower feeds an air chamber 63 which runsthe length and width of the backup plates 22 (FIGS. 1, 2, 3, and 7) inthe top and bottom carriages 35 and 25.

This air-bearing system minimizes the belt mold sliding-contact pressureagainst the slippery coated backup plates 59 and reduces wearing of thebelts and backup plate coating.

ELECTRIC SCREW JACKS

Electric screw jacks 56 (FIG. 1) and 32 (FIG. 8A) are used instead ofthe hydraulic equipment as is common in the art. This use of electricscrew jacks saves the energy required to continuously operate ahydraulic pump and motor. Electric screw jacks only operate (and only usenergy) when activated. The electrical screw jacks 56 and 32 provide amore positive and accurate movement of the machine components thanhydraulic cylinders and pistons. Because of their precise positioningthe movement of the machine components can be programmed to presetpositions when using electric screw jacks. The need for maintenance of ahydraulic pump, hydraulic connecting hose and tubing, valves, andcylinders is eliminated. This prior art maintenance is particularlysignificant since these hydraulic items must be maintained in aleak-free condition to prevent contamination of the molded product. Thecontinuous high decibel sound of a hydraulic pump is also eliminated bythe use of electric screw jacks.

The primary uses of the electrical screw jacks are:

1. Raise the top carriage 35 by jack 32 (FIG. 8A) to disengage the top34 and bottom 36 belt molds to facilitate changing the belt molds 34 and36. the top carriage 35 by jack 32 (FIG. 8A)

2. Lower the top carrier 35 by jack 32 (FIG. 8A) to form the moldchannel 33 (FIGS. 2 and 8B) for processing the resin feedstock.

3. Retract the grooved exit rolls 51 by jacks 56 (FIG. 1) to let thebelt molds 34 and 36 fall loose to facilitate changing the belt molds.

4. Extend the grooved exit rolls 51 to preset positions by jacks 56(FIG. 1) to put the belt molds 34 and 36 in tension as required for themolding operation.

5. Add extra tension to one belt mold 34 or 36 or the other tocompensate for small longitudinal mismatch of mold pattern, due to onebelt being slightly longer than the other This fine tuning isaccomplished by adjusting the electronic controllers for the screw jacks56 that set their stroke lengths.

6. Move the machine to and from the extruder as required to changeextruder dies and to adjust the distance between the extruder die andthe mold channel formed by the belt molds.

OPERATION AND FIBER BELT MOLD COOLING

In operation, as shown in FIGS. 1, 2, 8B, and 9, the continuously movingmold belts are mated and the top mold belt 34 is driven in an elongatedoval path around the top carriage 35, as indicated by the arrows 87(FIGS. 1 and 2). The bottom mold belt 36 is driven in a similarelongated oval path around the bottom carriage 25, as indicated by thearrows 88 (FIGS. 1 and 2). Thus, the mating molding surfaces 78 (FIG. 2)define a continuously moving molding channel 33 or, in some instances,more than one molding channel that provides a changing profile asdesired to produce a specific product configuration. The molding channel33 is continuously moving forward from the entry 89 (FIGS. 1 and 2) ofthe machine 30 to the machine exit 90 (FIG. 1).

The belt molds 34 and 36 are cooled by an air-cooling system in whichconditioned, i.e. cold air (35-50 degrees Fahrenheit), is blown onto andalong the molding surface 78 of the belt molds as the belts return fromthe exit end 90 to the entry end 89 of the machine 30 adjacent to theopen side of the insulated air-conditioning ducts 74 (FIGS. 1, 8A, and8B). The presently disclosed process and apparatus employ air cooling ofthe mold surfaces of the continuously moving flexible belt molds. Suchdry cooling of the mold surfaces is more compatible with the heatedthermoplastic materials being molded than is the us of cooling water onthe reverse surfaces of thin metal belts as used in the prior art. Thedirection and the volume of cold air passing over the belt molds 34 and36 are controlled by a series of hand adjustable dampers 75 (FIGS. 1,8A, and 8B) which control the direction, angle, velocity, amount, andperiod during the return from the exit to the entry end of the machine30.These dampers 75 have adjustment handles 75A (FIGS. 8A and 8B) whichcontrol the direction, angle, velocity, and amount of cold air duringthe return from the exit to the entry end of the machine 30. The coldair impinges the travelling hot belt molds. The dampers control thedirection and angle of the cold air to blow counter to the direction themolds are travelling and at the angle and velocity that optimizes theheat exchange. The amount of cold air and when the cold air contacts thetravelling hot belt mold surfaces are also controlled by the dampers.The dampers also provide the means to cool the surfaces of the hot beltmolds to a consistent temperature before the belt molds again contactthe hot plastic, thereby optimizing the molding conditions. In otherwords, it is desirable to have the temperature of the belt mold as itfirst encounters the hot plastic be uniform throughout a production run.The cold air in the ducts 74 is supplied by air conditioners 76 (FIGS.1, 8A, and 8B) of sufficient cooling capacity. The objective is toremove all of the surface heat that the belt molds 34 and 36 retain frombeing in contact with the hot (100-600 degrees Fahrenheit) moldableplastic material before the belt molds return to the entry 89 to againcontact the hot plastic.

When the hot plastic material 77 (FIGS. 2 and 8B) enters the moldchannel 33 (FIGS. 2 and 8B), it is formed by the pressure of the movingtop 34 and bottom 36 belt molds that are traveling around the entrydrive rolls 43. Shortly after the hot plastic 77 has been formed, thecold mold surfaces 78 (35-100 degrees Fahrenheit) of the silicone rubberbelt molds 39 and 40 chill the surface of the formed product in asimilar manner as the mold surfaces of injection molds and extrusiondies chill the surface of the products formed by these processes. Thecold rubber belt molds 39 and 40 chill the surface of the formedthermoplastic material 77 and such chilling then "sets" the exteriorregions of the molded plastic in its new, formed configuration. Duringthe time the silicone rubber belt molds 39 and 40 are in contact withthe hot plastic, these belt molds pick up heat, and the mold surface 78(FIGS. 2 and 8B) of each of the silicone rubber molds 34 and 36 becomeshot.

Because the silicone rubber molds 34 and 36 and fiber belts 37 and 38 ofthese belt molds 39 and 40 are poor thermal conductors, the belt molds39 and 40 do not transfer or absorb heat readily. As a practical matter,no significant amount of the heat penetrates through the thickness ofthe silicone rubber during any one contact of the travelling belt moldswith the hot plastic material 77. The heat retained by the belt molds issurface heat localized near the mold surfaces 78. The concentration ofheat near the mold surface 78 permits the use of a more efficientcooling system of blowing cold air directly over the mold surface 78 ofeach belt mold to remove this surface heat and to return the moldsurface 78 to a temperature of 35-100 degrees Fahrenheit before eachtravelling mold surface 78 again contacts the hot plastic 77.

The cold air in the ducts 74 is generated and blown by one or morecommercially available air conditioners 76 of sufficient capacity; e.g.,one ton to ten ton, connected to insulated ducts 74 that are as wide asthe belt molds 34 and 36. The open side of each duct 74 facing the hotmold surface 78 of the belt mold returning from the exit end to theentry end of the machine 3 is controlled with dampers 75 to direct thecold air against the hot mold surface 78 as required to remove thelocalized surface heat from the mold surface of the belt molds. Theair-conditioning units 76 are mounted near the entry end of the machineabove the returning top belt mold 34 and below the returning bottom beltmold 36 with the cold air traveling, as shown by the arrow 79 (FIGS. 1and 8B) against and opposite to the direction of travel of the movingreturning belts. Since the air-conditioner chilled, dry air is generallytraveling in a direction 79 counter to the direction of travel 87 and 88of the returning mold surface 78 from which heat is being extracted, wehave provided a counter-current-flow heat exchange, which we believe tobe an optimum flow relationship. An exhaust cold air flow 80 (FIG. 1)from the cold air ducts 74 (FIG. 1) is directed at the top and bottomsurfaces of the molded product 52 (FIG. 1) leaving the exit end of themachine 30.

As is well known, the amount of heat removed from a surface by the flowof a cooling fluid is dependent upon the velocity of the cooling fluidin relation to the heated surface. When the velocity of the flow of thecooling air 79 over the heated mold surface 78 is too low, the coolingair becomes saturated with heat and incapable of removing further heatfrom the heated surface prior to passing over the entire surface. Whenthe velocity of the cooling air relative to the heated surface is toohigh, the air conditioners 76 and their blowers are operating at a ratewhich exceeds optimum efficiency because the cooling air does not remainin contact with the heated surface long enough to absorb the greatestamount of heat possible. Therefore, a most efficient relative velocityexists wherein heat transfer from the mold surface 78 to the cooling air79 is maximized. The counter-current-flow of the present inventionattempts to maximize heat transfer efficiency from the belt molds 34 and36 to the cooling air by providing an optimal relative velocitytherebetween. This optimal relative velocity is achieved by the means ofadjustable dampers that cause the air to travel at a controlled velocityin a direction counter to the direction of travel of the mold surface78.

The cooling system described is a dry cooling system which is preferredto a wet or water-cooling system in a ho plastics molding operation. Theair-cooling system described here also eliminates the need for waterchillers, pumps, a recirculating system, a water cleaning system, and asump under the machine.

If the molded product 52 requires further cooling, it travels through awater bath, water spray, or through air-conditioning ducts 84 (FIG. 1).The cooled finished product "P" is cut at 85 to length, punched,slotted, painted, or has other finishing operations performed as ittravels over the conveyor system 53 (FIG. 1).

Electric screw jacks 81 (FIG. 1) move the machine 30 away from theextruder 28, as shown by the arrow 82 in FIG. 1, for service andmaintenance and for changing the extruder die 29. Electric screw jacks32 (FIG. 8A) move the top carriage up and down to change belt molds, asshown by the arrow 83 (FIG. 1).

FIG. 9 is a cross-sectional view of the complementary silicone rubbertop mold 39 and silicone rubber bottom mold 40, illustrating properalignment thereof. The continuously moving mold channel 33 forms a shapewhich correctly corresponds to the desired product.

FIG. 10 illustrates the effects of misalignment of the silicone rubbertop mold 30 relative to the silicone rubber bottom mold 40, thus causingundesired distortion of the mold channel 33. This results in distortionof the final molded product.

It is a function of the wide V-shaped ridges 41 and the V-shaped grooves42 as well as the crown on the grooved exit rolls to maintain properalignment of the silicone rubber top mold 39 relative to the siliconerubber bottom mold 40 and thereby prevent misalignment of thecontinuously moving mold channel 33.

The above-described process and apparatus has improved methods andcomponents to continuously produce impression-molded thermoplasticproducts with closer tolerances on a less costly machine. The machine iseasier to maintain, uses less energy, is less expensive to operate, andmakes less noise.

It is understood that the exemplary continuous molding process andapparatus described herein and shown in the drawings represents only apresently preferred embodiment of the invention. Indeed, variousmodifications and additions may be made to such embodiment withoutdeparting from the spirit and scope of the invention. For example, themolds may be comprised of flexible, heat-resistant materials other thansilicone rubber. Also, various arrangements of ducts providing coolingair to the mold surface are possible. Thus, these and othermodifications and additions may be apparent to those skilled in the artand may be implemented to adapt the present invention for use in avariety of applications.

What is claimed is:
 1. A process for three-dimensional forming ofthermoplastic material heated to a formable temperature comprising thesteps of:(a) providing a first flexible belt mold with an inner side andwith a first mold surface on an outer side, said first mold surfacehaving a first three-dimensional mold pattern therein; (b) providing asecond flexible belt mold with an inner side and with a second moldsurface on an outer side, said second mold surface having a secondthree-dimensional mold pattern therein; (c) providing first and secondspaced parallel longitudinally extending ridges on said inner side ofsaid first belt mold; (d) providing third and fourth spaced parallellongitudinally extending ridges on said inner side of said second beltmold; (e) positioning said first mold surface in juxtaposition with saidsecond mold surface with said first and second three-dimensional moldpatterns being in mating relationship for defining at least one moldchannel between said first and second mold surfaces; (f) revolving saidfirst and second flexible belt molds for moving said mold channel froman entrance region to an exit region; (g) introducing heatedthermoplastic material at moldable temperature into the entrance regionof the moving mold channel; (h) forming heated thermoplastic material insaid moving mold channel and removing heat therefrom for settingthermoplastic material in said moving mold channel into a formed producthaving a three-dimensional surface pattern exiting from the exit regionof the moving mold channel; (i) stabilizing said first flexible beltmold along said moving mold channel by a first backup plate extendinglongitudinally along the inner side of said first flexible belt mold;(j) guiding said first flexible belt mold by first and second spacedparallel clearances extending longitudinally along said first backupplate for receiving said first and second ridges, respectively; (k)stabilizing said second flexible belt mold along said moving moldchannel by a second backup plate extending longitudinally along theinner side of said second flexible belt mold; (l) guiding said secondflexible belt mold by third and fourth spaced parallel clearancesextending longitudinally along said second backup plate for receivingsaid third and fourth ridges, respectively; (m) introducing air betweenthe inner side of said first flexible belt mold and said first backupplate between said first and second ridges for providing an air-bearingeffect for reducing friction between the inner side of said firstflexible belt mold and said first backup plate; (n) introducing airbetween the inner side of said second flexible belt mold and said secondbackup plate between said third and fourth ridges for providing anair-bearing effect for reducing friction between the inner side of saidsecond flexible belt mold and said second backup plate; (o) blowing aironto said first mold surface for removing heat from said first moldsurface as said first flexible belt mold is returning from said exitregion to said entrance region; and (p) blowing air onto said secondmold surface for removing heat from said second mold surface as saidsecond flexible belt mold is returning from said exit region to saidentrance region.
 2. A process for three-dimensional forming ofthermoplastic material heated to a formable temperature as recited inclaim 1, including the further steps of:(a) introducing air between saidfirst and second ridges and said first and second clearances forproviding an air-bearing effect for reducing friction between said firstand second ridges and said first and second clearances; and (b)introducing air between said third and fourth ridges and said third andfourth clearances for providing an air-bearing effect for reducingfriction between said third and fourth ridges and said third and fourthclearances.
 3. A process for three-dimensional forming of thermoplasticmaterial heated to a formable temperature as recited in claim 2,including the further steps of:(a) shaping said first and secondclearances as first and second grooves, respectively, extending alongsaid first backup plate; (b) shaping said third and fourth clearances asthird and fourth grooves, respectively, extending along said secondbackup plate; (c) introducing air between said first and second ridgesand said first and second clearances by introducing air into said firstand second grooves through a plurality of apertures feeding air intosaid first and second grooves; and (d) introducing air between saidthird and fourth ridges and said third and fourth clearances byintroducing air into said third and fourth grooves through a pluralityof apertures feeding air into said third and fourth grooves.
 4. Aprocess for three-dimensional forming of thermoplastic material heatedto a formable temperature as recited in claim 1, including the furthersteps of:(a) providing said first and second ridges with first andsecond cog configurations, respectively; (b) providing said third andfourth ridges with third and fourth cog configurations, respectively;(c) revolving said first flexible belt mold by a first drive rollsprocket having first and second gear configurations matchingrespectively with said first and second cog configurations; and (d)revolving said second flexible belt mold by a second drive roll sprockethaving third and fourth gear configurations matching respectively withsaid third and fourth cog configurations, thereby maintaining matingrelationship of said first and second three-dimensional mold patterns onthe first and second revolving flexible belt molds by producingsimultaneous, equal forward motion of said first and second flexiblebelt molds.
 5. A process for three-dimensional forming of thermoplasticmaterial heated to a formable temperature recited in claim 1, includingthe further step of:(a) providing said first backup plate with a firstlow-friction coating facing the inner surface of said first flexiblebelt mold; (b) providing said second backup plate with a secondlow-friction coating facing the inner surface of said second flexiblebelt mold; (c) introducing air between the inner side of said firstflexible belt mold and said first backup plate between said first andsecond ridges by introducing air through a plurality of aperturesextending through said first backup plate and extending through saidlow-friction coating, said apertures feeding air into a region adjacentto the inner side of said first flexible belt mold between said firstand second ridges; and (d) introducing air between the inner side ofsaid second flexible belt mold and said second backup plate between saidthird and fourth ridges by introducing air through a plurality ofapertures extending through said second backup plate and extendingthrough said low-friction coating, said apertures feeding air into aregion adjacent to the inner side of said second flexible belt moldbetween said third and fourth ridges.
 6. Apparatus for three-dimensionalforming of thermoplastic material heated to a formable temperaturecomprising:(a) a first flexible belt mold with an inner side and with afirst mold surface on an outer side, said first mold surface having afirst three-dimensional mold pattern therein; (b) a second flexible beltmold with an inner side and with a second mold surface on an outer side,said second mold surface having a second three-dimensional mold patterntherein; (c) first and second spaced parallel longitudinally extendingridges on said inner side of said first belt mold; (d) third and fourthspaced parallel longitudinally extending ridges on said inner side ofsaid second belt mold; (e) carriage means for positioning said firstmold surface in juxtaposition with said second mold surface with saidfirst and second three-dimensional mold patterns being in matingrelationship for defining at least one mold channel between said firstand second mold surfaces; (f) drive means for revolving said first andsecond flexible belt molds for moving said mold channel from an entranceregion to an exit region; (g) feeding means for introducing heatedthermoplastic material at moldable temperature into the entrance regionof the moving mold channel; (h) the first and second three-dimensionalmold patterns of said first and second mold surfaces forming heatedthermoplastic material in said moving mold channel and removing heattherefrom for setting thermoplastic material in said moving mold channelinto a formed product having three-dimensional surface patterns exitingfrom the exit region of the moving mold channel; (i) said first flexiblebelt mold being stabilized along said moving mold channel by a firstbackup plate extending longitudinally along the inner side of said firstflexible belt mold; (j) said first flexible belt mold being guided byfirst and second spaced parallel clearances extending longitudinallyalong said first backup plate for receiving said first and secondridges, respectively; (k) said second flexible belt mold beingstabilized along said moving mold channel by a second backup plateextending longitudinally along the inner side of said second flexiblebelt mold; (l) said second flexible belt mold being guided by third andfourth spaced parallel clearances extending longitudinally along saidsecond backup plate for receiving said third and fourth ridges,respectively; (m) air feeding means for introducing air between theinner side of said first flexible belt mold and said first backup platebetween said first and second ridges for providing an air-bearing effectfor reducing friction between the inner side of said first flexible beltmold and said first backup plate; (n) air feeding means for introducingair between the inner side of said second flexible belt mold and saidsecond backup plate between said third and fourth ridges for providingan air-bearing effect for reducing friction between the inner side ofsaid second flexible belt mold and said second backup plate; (o) airblowing means directing air onto said first mold surface for removingheat from said first mold surface as said first flexible belt mold isreturning from said exit region to said entrance region; and (p) airblowing means directing air onto said second mold surface for removingheat from said second mold surface as said second flexible belt mold isreturning from said exit region to said entrance region.
 7. Apparatusfor three-dimensional forming of thermoplastic material heated to aformable temperature as recited in claim 6, further comprising:(a) meansfor introducing air between said first and second ridges and said firstand second clearances for providing an air-bearing effect for reducingfriction between said first and second ridges and said first and secondclearances; and (b) means for introducing air between said third andfourth ridges and said third and fourth clearances for providing anair-bearing effect for reducing friction between said third and fourthridges and said third and fourth clearances.
 8. Apparatus forthree-dimensional forming of thermoplastic material heated to a formabletemperature as recited in claim 7, in which:(a) said first and secondclearances are first and second grooves, respectively, extending alongsaid first backup plate; (b) said third and fourth clearances are thirdand fourth grooves, respectively, extending along said second backupplate; (c) air is introduced between said first and second ridges andsaid first and second clearances by introducing air into said first andsecond grooves through a plurality of apertures feeding air into saidfirst and second grooves; and (d) air is introduced between said thirdand fourth ridges and said third and fourth clearances by introducingair into said third and fourth grooves through a plurality of aperturesfeeding air into said third and fourth grooves.
 9. Apparatus forthree-dimensional forming of thermoplastic material heated to a formabletemperature as recited in claim 6, in which:(a) said first and secondridges have first and second cog configurations, respectively; (b) saidthird and fourth ridges have third and fourth cog configurations,respectively; (c) said first flexible belt mold is revolved by a firstdrive roll sprocket having first and second gear configurations matchingrespectively with said first and second cog configurations; and (d) saidsecond flexible belt mold is revolved by a second drive roll sprockethaving third and fourth gear configurations matching respectively withsaid third and fourth cog configurations, thereby maintaining matingrelationship of said first and second three-dimensional mold patterns onthe first and second revolving flexible belt molds by producingsimultaneous, equal forward motion of said first and second flexiblebelt molds.
 10. Apparatus for three-dimensional forming of thermoplasticmaterial heated to a formable temperature recited in claim 6, inwhich:(a) said first backup plate has a first low-friction coatingfacing the inner surface of said first flexible belt mold; (b) saidsecond backup plate has a second low-friction coating facing the innersurface of said second flexible belt mold; (c) air is introduced betweenthe inner side of said first flexible belt mold and said first backupplate between said first and second ridges by a plurality of aperturesextending through said first backup plate and extending through saidlow-friction coating feeding air into a region adjacent to the innerside of said first flexible belt mold between said first and secondridges; and (d) air is introduced between the inner side of said secondflexible belt mold and said second backup plate between said third andfourth ridges by a plurality of apertures extending through said secondbackup plate and extending through said low-friction coating feeding airinto a region adjacent to the inner side of said second flexible beltmold between said third and fourth ridges.
 11. A process forthree-dimensional forming of thermoplastic material heated to a formabletemperature comprising the steps of:(a) providing a first flexible fiberbelt mold with an inner side and with a first mold surface on an outerside, said first mold surfaces having a first three-dimensional moldpattern therein; (b) providing a second flexible fiber belt mold with aninner side and with a second mold surface on an outer side said secondmold surface having a second three-dimensional mold pattern therein; (c)positioning said first mold surface in juxtaposition with said secondmold surface with said first and second three-dimensional mold patternsbeing in mating relationship for defining at least one mold channelbetween said first and second mold surfaces; (d) applying tension tosaid first and second flexible fiber belt molds; (e) revolving saidfirst and second flexible fiber belt molds while in tension for movingsaid mold channel from an entrance region to an exit region; (f)introducing heated thermoplastic material at moldable temperature intothe entrance region of the moving mold channel; (g) forming heatedthermoplastic material in said moving mold channel and removing heattherefrom for setting thermoplastic material in said moving mold channelinto a formed product having a three-dimensional surface pattern exitingfrom the exit region of the moving mold channel; (h) stabilizing saidfirst flexible fiber belt mold along said moving mold channel by a firstbackup plate extending longitudinally along the inner side of said firstflexible belt mold; (i) laterally guiding said first flexible fiber beltmold moving along said first backup plate; (j) stabilizing said secondflexible fiber belt mold along said moving mold channel by a secondbackup plate extending longitudinally along the inner side of saidsecond flexible belt mold; (k) laterally guiding said second flexiblefiber belt mold moving along said second backup plate; (l) introducingair between the inner side of said first flexible fiber belt mold andsaid first backup plate for providing an air-bearing effect for reducingfriction between the inner side of said first flexible fiber belt moldand said first backup plate; (m) introducing air between the inner sideof said second flexible fiber belt mold and said second backup plate forproviding an air-bearing effect for reducing friction between the innerside of said second flexible fiber belt mold and said second backupplate; (n) applying extra tension in one revolving flexible fiber beltmold relative to tension in the other revolving flexible fiber belt moldfor fine tuning the mating of said first and second three-dimensionalmold patterns for compensating for small longitudinal mismatching of thefirst and second three-dimensional mold patterns due to a slightdifference in the length of the first and second revolving flexiblefiber belt molds; (o) blowing air onto said first mold surface forremoving heat from said first mold surface as said first flexible fiberbelt mold is returning from said exit region to said entrance region;and (p) blowing air onto said second mold surface for removing heat fromsaid second mold surface as said second flexible fiber belt mold isreturning from said exit region to said entrance region.
 12. A processfor three-dimensional forming of thermoplastic material heated to aformable temperature as claimed in claim 11, including the further stepsof:(a) revolving said first flexible fiber belt mold past a first exitroll positioned near said exit region of the moving mold channel; (b)revolving said second flexible fiber belt mold past a second exit rollpositioned near said exit region of the moving mold channel; (c)actuating a first pair of electric screw jacks for shifting said firstexit roll in a direction away from said entrance region for applyingtension to said first flexible fiber belt mold; (d) actuating a secondpair of electric screw jacks for shifting said second exit roll in adirection away from said entrance region for applying tension to saidsecond flexible fiber belt mold; and (e) adjusting relative strokes ofsaid first and second pairs of screw jacks for applying extra tension inone revolving flexible fiber belt mold relative to the other revolvingflexible fiber belt mold for fine tuning the mating of said first andsecond three-dimensional mold patterns.
 13. A process forthree-dimensional forming of thermoplastic material heated to a formabletemperature as claimed in claim 11, including the further steps of:(a)controlling air blown onto said first mold surface for controllablyremoving heat from said first mold surface; (b) controlling air blownonto said second mold surface for controllably removing heat from saidsecond mold surface; and (c) regulating the air blown onto said firstand second mold surfaces for producing consistent surface temperature inthe first and second mold surfaces as they come into contact with heatedthermoplastic material being introduced into said entrance region, saidconsistent surface temperature being uniform throughout a productionrun.
 14. Apparatus for three-dimensional forming of thermoplasticmaterial heated to a formable temperature comprising:(a) a firstflexible fiber belt mold with an inner side and with a first moldsurface on an outer side, said first mold surface having a firstthree-dimensional mold pattern therein; (b) a second flexible fiber beltmold with an inner side and with a second mold surface on an outer side,said second mold surface having a second three-dimensional mold patterntherein; (c) carriage means for positioning said first mold surface injuxtaposition with said second mold surface with said first and secondthree-dimensional mold patterns being in mating relationship fordefining at least one mold channel between said first and second moldsurfaces; (d) first and second tension applying means for applyingtension respectively to said first and second flexible fiber belt molds;(e) drive means for revolving said first and second flexible fiber beltmolds while in tension for moving said mold channel from an entranceregion to an exit region; (f) heated thermoplastic feeding means forintroducing heated thermoplastic material at moldable temperature intothe entrance region of the moving mold channel; (g) said first andsecond three-dimensional mold patterns of said first and second moldsurfaces forming heated thermoplastic material in said moving moldchannel and removing heat from the thermoplastic material in said movingmold channel for setting thermoplastic material in said moving moldchannel into a formed product having a three-dimensional surface patternexiting from the exit region of the moving mold channel; (h) a firstbackup plate for stabilizing said first flexible belt mold along saidmoving mold channel, said first backup plate extending longitudinallyalong the inner side of said first flexible belt mold; (i) lateral guidemeans for laterally guiding said first flexible fiber belt mold movingalong said first backup plate; (j) a second backup plate for stabilizingsaid second flexible belt mold along said moving mold channel, saidsecond backup plate extending longitudinally along the inner side ofsaid second flexible belt mold; (k) lateral guide means for laterallyguiding said second flexible fiber belt mold moving along said secondbackup plate; (l) first air feeding means for introducing air betweenthe inner side of said first flexible belt mold and said first backupplate for providing an air-bearing effect for reducing friction betweenthe inner side of said first flexible fiber belt mold and said firstbackup plate; (m) second air feeding means for introducing air betweenthe inner side of said second flexible belt mold and said second backupplate for providing an air-bearing effect for reducing friction betweenthe inner side of said second flexible fiber belt mold and said secondbackup plate; (n) control means for said first and second tensionapplying means for applying extra tension to one revolving flexiblefiber belt mold relative to tension in the other revolving flexiblefiber belt mold for fine tuning the mating of said first and secondthree-dimensional mold patterns for compensating for small longitudinalmismatching of the first and second three-dimensional mold patterns dueto a slight difference in the length of the first and second revolvingflexible fiber belt molds; (o) first air blowing means directing aironto said first mold surface for removing heat from said first moldsurface as said first flexible belt mold is returning from said exitregion to said entrance region; and (p) second air blowing meandirecting air onto said second mold surface for removing heat from saidsecond mold surface as said second flexible belt mold is returning fromsaid exit region to said entrance region.
 15. Apparatus forthree-dimensional forming of thermoplastic material heated to a formabletemperature as recited in claim 14, further comprising:(a) a first exitroll positioned near said exit region of the moving mold channel onwhich revolves said first flexible fiber belt mold ; (b) a second exitroll positioned near said exit region of the moving mold channel onwhich revolves said second flexible fiber belt mold; (c) said firsttension applying means including a first pair of electric screw jackscoupled to opposite ends of said first exit roll for shifting said firstexit roll in a direction away from said entrance region for applyingtension to said first flexible fiber belt mold; (d) said second tensionapplying means including a second pair of electric screw jacks coupledto opposite ends of said second exit roll for shifting said second exitroll in a direction away from said entrance region for applying tensionto said second flexible fiber belt mold; and (e) control means for saidfirst and second pairs of screw jacks for adjusting relative strokes ofsaid first and second pairs of screw jacks for applying extra tension inone revolving flexible fiber belt mold relative to the other revolvingflexible fiber belt mold for fine tuning the mating of said first andsecond three-dimensional mold patterns.
 16. Apparatus forthree-dimensional forming of thermoplastic material heated to a formabletemperature as recited in claim 14, further comprising:(a) first aircontrol means for controlling air blown onto said first mold surface;(b) second air control means for controlling air blown onto said firstmold surface; and (c) regulating means for regulating the first andsecond air control means for producing consistent surface temperature inthe first and second mold surfaces as they come into contact with heatedthermoplastic material being introduced into said entrance region, saidconsistent surface temperature being uniform throughout a productionrun.
 17. Apparatus for forming products with surfaces havingthree-dimensional configurations from thermoplastic material heated to aformable temperature comprising:(a) a first flexible fiber belt moldwith an inner side and with a first mold surface on an outer side, saidfirst mold surface having a first three-dimensional mold patterntherein; (b) a second flexible fiber belt mold with an inner side andwith a second mold surface on an outer side, said second mold surfacehaving a second three-dimensional mold pattern therein; (c) carriagemeans for positioning said first mold surface in juxtaposition with saidsecond mold surface with said first and second three-dimensional moldpatterns being in mating relationship for defining at least one moldchannel between said first and second mold surfaces; (d) drive means forrevolving said first and second flexible fiber belt molds on saidcarriage means with said first and second three-dimensional moldpatterns being in mating relationship for moving said mold channel froman entrance region to an exit region; (e) a first exit roll mounted atits opposite ends on movable bearings on said carriage means and beingpositioned near said exit region of the moving mold channel on whichrevolves said first flexible fiber belt mold; (f) a second exit rollmounted at its opposite ends on movable bearing on said carriage meansand being positioned near said exit region of the moving mold channel onwhich revolves said second flexible fiber belt mold; (g) a first pair ofscrew jacks coupled to said bearings at opposite ends of said first exitroll for shifting said first exit roll in a direction away from saidentrance region for applying tension to said first flexible fiber beltmold; (h) a second pair of screw jacks coupled to said bearings atopposite ends of said second exit roll for shifting said second exitroll in a direction away from said entrance region for applying tensionto said second flexible fiber belt mold; (i) said drive means revolvingsaid first and second fiber belt molds on said carriage means with saidfirst and second fiber belt molds being in tension and with said firstand second three-dimensional mold patterns being in mating relationship;(j) operating means for said first and second pairs of screw jacks forrelatively shifting in a direction away from said entrance region saidbearing means for said first and second exit rolls for applying extratension in one revolving flexible fiber belt mold relative to tension inthe other revolving flexible fiber belt mold to compensate for saidother being a slightly longer belt mold for fine tuning the mating ofsaid first and second three-dimensional mold patterns; (k) a firstbackup plate for stabilizing said first flexible belt mold along saidmoving channel, said first backup plate extending longitudinally alongthe inner side of said first flexible belt mold; (l) first guide meansfor laterally guiding said first flexible belt mold moving along saidfirst backup plate; (m) a second backup plate for stabilizing saidsecond flexible belt mold along said moving mold channel, said secondbackup plate extending longitudinally along the inner side of saidsecond flexible belt mold; (n) second guide means for laterally guidingsaid second flexible belt mold moving along said second backup plate;(o) first air-bearing means for introducing air between the inner sideof said first flexible belt mold and said first backup plate forproviding an air-bearing effect for reducing friction between the innerside of said first flexible belt mold and said first backup plate; (p)second air-bearing means for introducing air between the inner side ofsaid second flexible belt mold and said second backup plate forproviding an air-bearing effect for reducing friction between the innerside of said second flexible belt mold and said second backup plate; (q)said first and second three-dimensional mold patterns of said first andsecond mold surfaces being for forming heated thermoplastic material insaid moving mold channel and for removing heat from the thermoplasticmaterial in said moving mold channel for setting thermoplastic materialin said moving mold channel for forming a product with surfaces havingthree-dimensional configurations exiting from the exit region of themoving mold channel; (r) first air directing means for directing blownair onto said first mold surface for removing heat from said first moldsurface as said first flexible belt mold is returning from said exitregion to said entrance region; and (s) second air directing means fordirecting blown air onto said second mold surface for removing heat fromsaid second mold surface as said second flexible belt mold is returningfrom said exit region to said entrance region.